‘The next time you see the full moon high in the south, look carefully at its right-hand edge and let your eye travel upward along the curve of the disk. Round about two o’clock you will notice a small, dark oval: anyone with normal eyesight can find it quite easily. It is the great walled plain, one of the finest on the Moon, known as the Mare Crisium – the Sea of Crises. Three hundred miles in diameter, and almost completely surrounded by a ring of magnificent mountains, it had never been explored until we entered it in the late summer of 1996.’

When Arthur C Clarke wrote the opening paragraph of The Sentinel in 1948, he can’t have known it was going to define his career. It didn’t even get published for three years, which was a substantial delay then even if it’s not unusual now.

The true significance of the story is not apparent until Wilson, the protagonist, climbs one of the mountains surrounding the Mare Crisium and finds himself on a plateau that ‘ had been leveled to support a glittering, roughly pyramidal structure, twice as high as a man, that was set in the rock like a gigantic, many-faceted jewel’.

Clarke was an enormously prolific writer, producing enough stories, novels and screenplays for several careers. The pyramid sentinel, transformed into an obelisk, lay at the centre of his best known work, the Space Odyssey series. The final volume, 3001: The Final Odyssey, was published in 1997, a year later than The Sentinel was set.

Just after its publication, the 79-year old Clarke Clarke was interviewed by Roger Ebert. Although Clarke lived for another decade, he wrote very little after 3001, so the interview is something of a retrospective of his career:

An odyssey in science and literature

By the standards of science fiction series like Anne McCaffrey’s Dragons of Pern or Robert Jordan’s Wheel of Time, Space Odyssey’s two films and four novels look fairly limited in volume. However, there are two reasons why it became the classic it remains. The first is the film that Clarke collaborated with Stanley Kubrick to produce. Far more people watch science fiction films than read science fiction novels, so Kubrick took the Space Odyssey to a much wider audience than it would have reached if it had stayed on paper.

Still from 2001: A Space Odyssey (Bill Lile [CC / Flickr])

The second is that in the nearly 50 years between The Sentinel and 3001, each novel contained the latest speculations on life in the solar system and beyond. Clarke went so far as to move the principal site of action from Saturn’s moon Titan in the novel and film 2001: A Space Odyssey, released in 1968, to Jupiter’s moon Europa in 2010: Odyssey Two, released in 1983. The reason for the change was that in 1979, Voyager 1’s photographs of Europa showed a surface of water ice, implying the presence of an ocean. In the same year, Pioneer 11 showed that Titan’s surface is almost cold enough to freeze nitrogen, making it unlikely that the chemistry necessary for life could have taken place.

The combined observations made it look far more likely for life to arise on Europa than Titan, although the complex organic chemistry of Titan’s atmosphere still makes it one of the more likely candidates in the solar system.

Alien intelligence and artificial intelligence

While the main theme of Space Odyssey is the origin of life beyond earth and the reasons why we have yet to find – or be found by – any, the most discussed character of 2001 was not alive at all. Actor Douglas Rain voiced the computer HAL 9000 with comforting tones that send shivers down the spine as HAL turns homicidal. It’s impossible to forget the words, ‘I’m sorry, Dave. I’m afraid I can’t do that’, once you’ve heard them.

The Space Odyssey series of novels (Gary Martin [CC / Flickr])

Among the various questions that HAL has raised is whether his rebellion was a malfunction or a consequence of careless programming. HAL may have simply decided his human crew were in the way of the objectives he had been programmed to prioritise.

Clarke’s response when Ebert put the question to him, ‘I think I’ll take a pass on that one’, invites HAL’s devotees to draw their own conclusions. With artificial intelligence far more advanced now than it was when we were introduced to HAL in 1968, the hypothesis that HAL was doing exactly what he had been programmed to do had become a much used example of the dangers of giving AI too much autonomy when controlling potentially dangerous systems, which I pontificated about in detail a few months ago.

In the interview, Clarke says artificial intelligence is always twenty years in the future, a common schedule for technological breakthroughs. Now that nearly 20 years have passed since the interview, AI may not be able to understand a verbal instruction to open the pod bay doors well enough to refuse it but could carry out most of his other tasks. In other words, the things that made HAL dangerous. The concerns about artificial intelligence that Clarke raised nearly 50 years ago are finally becoming contemporary.

Behind Clarke’s schedule

Still from 2001: A Space Odyssey (Bill Lile [CC / Flickr])

In other respects, Clarke’s predictions about timing proved as optimistic as most predictions about space exploration in the 1950s and 1960s. The large expedition that got Wilson to the moon in 1996 would have been feasible technologically, but the early 1970s saw the death of interest in manned lunar exploration by any organisation capable of funding it. We have never succeeded in getting anyone beyond low earth orbit without an enormous expenditure of resources.

Arguably, we now know considerably more about the solar system than we would have done if manned expeditions had been a priority. Expanding the scale of manned lunar missions, by NASA or any other agency, would have absorbed the resources that have been spent on unmanned probes. Advances in robotics have taken us far beyond what Clarke could have predicted in 1948, or even 1968. Robots weigh less than people and can range across the solar system without needing food, water or oxygen. The modern equivalent of HAL could be sent off without needing to take any astronauts with him, although we could still not expect one to understand a verbal instruction to open the pod bay doors.

Perhaps HAL had a point when he decided he could carry out the mission better on his own.

By 2001 and 2010, when Space Odyssey described respectively a two man mission to Titan and a race between large American, Soviet and Chinese missions to Europa, manned spaceflight was restricted to low earth orbit. Since then, the Huygens probe has landed on Titan. NASA proposes the Europa Clipper to explore Europa, which may include an ESA-built lander.

However, the science fiction of the foreseeable future is about possibilities rather than predictions. Space Odyssey was based on what appeared possible at the time rather than what appeared likely. If the Apollo missions had found an obelisk that could only have been put there by an alien civilisation, it would have pushed exploring the solar system up the priority list of every government with a large enough budget to do anything about it.

Anybody out there?

More intriguingly, it is impossible to rule out the possibility that an alien artefact may yet be discovered in the solar system. The alien intelligence of The Sentinel because they surmised that the moon would be the first place our species explored once we developed the ability to explore beyond our own planet. They, or rather the author who conceived it, were correct. No sooner had the Soviet Union put a satellite in orbit than everyone engaged in spaceflight found themselves engaged in racing for the moon.

For a work of fiction, it made sense for Clarke to place the artefact in a place that would soon be within our ability to find. An alien civilisation would not be constrained by such concerns. Given that travel between solar systems would take years, any species that achieved it would have to adapt itself to the environment of interstellar spaceflight. Such a species may prefer to avoid the intense solar radiation of the inner solar system as much as it would not want to have to clamber back out of earth’s deep gravity well. If they have any reason for entering the solar system at all, they may well confine themselves to the outer planets and asteroids where we have only sent a few probes that are very limited in what they can observe.

Unless such an artefact demanded attention loudly enough to be heard from one plantary orbit to another, we would not have found it. A civilisation that spans the light years between stars is unlikely to be impressed by a few footprints on our nearest large satellite and the occasional robot taking snapshots beyond that. A device with the intent of Clarke’s sentinel is as likely to be found on Neptune’s moon Triton as on our own.

Our solar system could be full of alien artefacts, each ‘patiently signaling the fact that no one had discovered it’ as Clarke puts it in The Sentinel.

4 comments on “Greater Minds: Arthur C Clarke looks back”

Thanks for posting this. It’s very nice to think about Arthur Clarke again. Yesterday we went looking for the Chelsea Hotel where Clarke was based when he wrote 2001, sadly it is currently closed for renovation!

Profiles of the Future,which Clarke mentions in the video clip, is an essential collection of ideas which no SF writer should be without! (don’t know what happened to my copy!). The Time Probe, which Clarke mentions in the clip, was a means of viewing the past. I can’t recall any story where such a device was mentioned but it might be worth thinking about how it might be deployed in fiction.

Thanks for the thoughts. To my shame, I haven’t read Profiles of the Future which I really must do. The time probe sounds very like the idea at the centre of Ken Liu’s ‘The Man Who Ended History’ (http://kenliu.name/binary/liu_the_man_who_ended_history.pdf), which got Hugo and Nebula nominations a few years ago.

I’m sure there are plenty more stories that can be based around it though.

Thanks for the Ken Liu, very nicely done. I particularly enjoyed the way he used the destructive nature of archeological digging to support his destructive, (read once only and can’t record) time probe. It made the tale work somehow.

Re-reading the Clarke again, I’d forgotten how much he disliked the motor car (and this in the days before climate change came on the radar) he makes amusing reading. He’s well wide of the mark with his enthusiasm for hovercraft though.

But Clarke has a fine touch with analogy. Check out his thoughts on Roman sundials and how they gave a variable nature to the passage of time throughout the day. This made life very difficult for clockmakers who had to try and mirror this variable nature using mechanics. This put me in mind of those people who gripe that you cannot refuel an electric vehicle in 5 minutes at any gas station while overlooking the fact that such a vehicle doesn’t even need a special purpose refuelling station.